No error for ServiceServer on duplicate topic

[broesdecat]

Hi,

I observed the following:

• a serviceserver A running on servicename X, which is properly receiving calls from a serviceclient
• another serviceserver B is started, accidentally also on X
• logging info reports initialization of B as succesful, neither does any other node complain
• messages sent by the client keep arriving only at A

Is this the expected behavior?

Thanks!
Broes

[jubeira]

Hi @broesdecat,

Thanks for the observation. It doesn't look like expected behavior to me; at least I would expect some sort of warning/ error message. Ideally, the behavior should be the same as in rospy or roscpp (I would start by checking that).

If this is a problem for you, feel free to open a PR with a proposed fix. Otherwise, I will take a look when I have some time (it might take a bit long).

[SpyrosKou]

Hi,
I would like to add some information on this issue.

When the two service servers A and B that have the same service name X are started on the same Node the issue does not occur. I only occurs when service servers A and B are started on different Nodes.
When the two service servers are started on the same Node a DuplicateServiceException is thrown.

The existence of two service servers A and B using the same service name X on the same Node is tested in org.ros.node.service.ServiceIntegrationTest.

The rosjava MasterServer when a new service B is registered that uses an existing service name X, unregisters the previous service instance A and registers the new one (B) under the same name (X), Assuming (as written in the comments) that the service instance A was stopped and the new service server B replaces it.

However the following are also valid:

1. The MasterServer does not stop node with service server A when a new Service Server B with the same name apperas. So if Service Server A with Service Name X was not stopped as assumed, the server will be still running.
2. The old clients that have already been created to call Service Server A are not informed
3. Creating new clients from a new node actually seems to still contact ServiceServer A although Service Server B should be contacted.

Best regards,
Spyros